Polymer alloys composed of two resin components include an immiscible blend, a miscible blend, and a partially miscible blend. In a miscible blend, two resin components are miscible with each other in the practical range from the glass transition temperature to the thermal decomposition temperature. In an immiscible blend, two resin components are immiscible with each other over the range. In a partially miscible blend, two resin components are miscible with each other in a certain range but are in a phase separation state in a different range so that spinodal decomposition occurs. In general, miscible-type polymer alloys often have intermediate properties between those of resin components blended, because the components are dissolved in molecular order to each other. To take advantage of the properties of two resin components, therefore, studies on immiscible or partially miscible-type polymer alloys have been actively conducted.
Japanese Patent Application Laid-Open (JP-A) No. 2003-286414 discloses that a both-phase continuous structure with a structure cycle of 0.001 to 1 μm or a dispersion structure with an inter-particle distance of 0.001 to 1 μm is formed through spinodal decomposition using polycarbonate resin and polybutylene terephthalate resin, so that mechanical strength is improved. The method disclosed in JP '414 includes making polycarbonate resin and polybutylene terephthalate resin miscible with each other by applying shearing to them in an extruder, and then allowing spinodal decomposition to occur to form an alloy structure. The method disclosed in JP '414 has the limit that when a combination of generally immiscible resins is used, it is impossible to form a both-phase continuous structure with a structure cycle of 0.001 to 1 μm or a dispersion structure with an inter-particle distance of 0.001 to 1 μm. The method disclosed in JP '414 also has a problem in which it is difficult to uniformly apply shearing, so that the dispersed phase uniformity is low.
International Patent Application Publication No. 2009/041335 discloses that a polymer alloy composed of thermoplastic resin components and having a fine and uniformly controlled structure is obtained by a process including: providing an oligomer or a monomer as a precursor of at least one of the thermoplastic resin components so that the remaining thermoplastic resin component provided is miscible with the oligomer or the monomer; and inducing spinodal decomposition by chemical reaction in the coexistence of two resins. Further, in the method disclosed in WO '335, a precursor of at least one thermoplastic resin component and the remaining thermoplastic resin component must be miscible with each other. Therefore, it has the limit that a both-phase continuous structure with a structure cycle of 0.001 to 1 μm or a dispersion structure with an inter-particle distance of 0.001 to 1 μm cannot be formed using a combination of immiscible resins.
On the other hand, concerning immiscible-type polymer alloy, which generally has spherical dispersed particles with a size of 1 μm or more, attempts to reduce the dispersed particle size have also been made in recent years.
JP-A No. 2009-46641 discloses that when an immiscible polymer alloy composed of polyether imide resin and polyphenylene sulfide resin is produced, the number average particle size of the dispersed particles is reduced to 1,000 nm or less by increasing the shear force during compounding process or by adding a compatibilizer, so that the toughness is improved. The method disclosed in JP '641, in which the resulting structure contains spherical dispersed particles, is not sufficiently effective in improving heat resistance.
It could therefore be helpful to provide polymer alloys that also have transparency while maintaining the original good heat resistance and mechanical properties of the resins blended.